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Viewing available space on iPhone

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Q: How accurate is the available space info on the built in iPhone Settings app? I have an 8GB iPhone 3G and am very conscious of how little space 8GB has become. I have tried a number of different available space apps and they all seem to provide different answers. I like DiskBadge because I don’t have to run it to see how much space is available. The Available Memory App shows good information including how many songs, movies, TV shows and images you can still store and Disc Space just shows total capacity, used and available space with a pie graph. But it seems to show more available room than the others do. For example the built in Settings app shows 1.4 GB and Disc Space shows 1.53, Disk Badge shows 1.54 GB and Available Memory shows 1.4 GB. It seems like there’s a big rounding error somewhere. It is not a huge difference across the board but I would like to find an app that is accurate about how much space I have left on my iPhone.

- Thom

A: As a rule, the available space information found in the Settings app is the most accurate as it’s core to the iOS system. Third-party applications should report the same values, all other things being equal, but since you’re relying on a third-party developer it’s possible that there could be bugs or other problems in these applications that may report the free space incorrectly.

However, another reason you could be seeing a discrepancy is that the amount of free space on your device is not as static as you may expect. Applications consume space and write data to the storage on your iPhone in the same manner as they do on a desktop computer, and although iOS doesn’t use virtual memory (ie, swap files), apps themselves may still have their own storage caches, not to mention apps like Mail and Safari which download mail and cache web pages—sometimes even when you’re not actively using them.

You may also want to compare these numbers to what iTunes reports in its capacity bar when you connect your iPhone to your computer, which also breaks down how much space is used by different types of data.

Keep in mind as well that third-party apps cannot continue running in the background except for very specific functions, which do not include monitoring storage capacity. Therefore, apps like Disk Badge cannot actually update your available space unless you open them—what you see on the home screen will be a static number that indicates the amount of space that was available on your device the last time you opened the app.